Reusable casks, also known as kegs, are known in the beverage industry. Once a cask's liquid contents have been removed, it is usual to clean its interior so that it can be re filled with liquid contents. This removes any product residues in the cask's interior. A known cleaning method is a CIP method.
Cleaning requires a number of evacuating steps. These steps involve evacuating product residues and cleaning or rinsing fluids from a reusable cask's interior. It is usual for these evacuating steps to be assisted by compressed air. In particular, it is common to pressurize, or pre tension the cask's interior with compressed air to force out any fluid present in the cask's interior.
A disadvantage of the prior art is that compressed air is frequently only available at the cleaning device at a certain pre-determined operating pressure. This pressure is often such as to promote only an inadequate and time-consuming expulsion of the fluid present in the reusable cask. The energy efficiency of the compressed air-based pumping principle known from the prior art is also poor.